It seems to me like a pretty fundamental assumption of the contango trade described in that article, is that demand will be flat to up (maybe slightly down) over the next year or 5 (depends over what time period you're doing this trade over). The other half of this trade is that you sell today the oil you'll be delivering in 6 months or whatever time period you're going to deliver the oil. Which means you're shifting the problem of what the oil price will be in 6 months (or whatever) to the futures market. And today, the futures market is pricing in a big jump in the price of oil in 6 months (or whatever time period you care for).
What makes this trade work is that you can sell future oil today for a big premium over what you can buy physically delivered oil today. So much more that you can hire an oil tanker to load up and sit with 2M bbl oil for that 6 months, and then deliver the oil to the person that buys your future contract today.
The contango trader, as long as the counter parties don't go bankrupt, is getting risk free return.
So the answer to your question - that's all well and good, but what if ... The people playing the oil futures market are gonna get burned. Those people are buying future delivered oil at a big premium to today's oil. They're gonna be in big trouble if today's low prices are here to stay. Of course, they're betting that future oil, even at the elevated prices they're aiming for, is going to be even higher. Sounds like the fundamental market is changing, and the people playing in that market are still working off the old playbook for making money in oil
I hadn't really thought of this - the contango traders are selling future oil today. They're competing with producers of oil that want to hedge their future production. That looks like the makings of a crowded future trade to me. With so many sellers of future oil, that looks to me like those future prices are going to start coming down and get closer to oil delivered today.